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Radiative coupling of objects with outer space, through the atmospheric spectral transparency window, allows passive cooling below ambient temperature. Such passively created cold sinks can be used for converting ambient heat into other useful forms of energy. Using this approach, conversion of ambient heat to electricity has been demonstrated in macroscopic settings, where the radiatively cooled heat sink is a macroscopic object coupled with ambient heat through a heterogeneously attached, standalone, thermoelectric generator. In contrast, miniaturization and on-chip integration of such heat engines has not been demonstrated, although it could be useful in portable remote technological applications. Such integration would first require that both the radiatively cooled heat sink and the hot (ambient temperature) side of the engine are monolithically integrated on a single chip. This first step is the focus of our work: we demonstrate the creation of a local thermal gradient on-chip by radiative cooling of a 90 nm thick freestanding silicon nitride nanomechanical resonator integrated on a silicon substrate that remains at ambient temperature. The reduction in temperature of the thin film is inferred by tracking its mechanical resonance frequency, under high vacuum, using an optical fiber interferometer. Experiments were conducted on 15 different days during fall and summer months, under various solar illumination, resulting in successful radiative cooling of the membrane in each case. Maximum temperature drops of 9.3 K and 7.1 K are demonstrated during the day and night, respectively, in close correspondence with our heat transfer model. Future improvements to the experimental setup could improve the temperature reduction to 48 K for the same membrane, while emissivity engineering potentially yields a maximum theoretical cooling of 67 K with an ideal emitter.

The reaction of a tethered pyridine diimine (PDI) ligand with copper(I) chloride yielded a μ-chlorido bridged cationic dicopper(I) PDI complex, which is a rare structural motif. The geometric constraint of the ligand is fostering attractive van der Waals interactions between the coplanar pyridine units. This is supported by an Atoms in Molecules (AIM) and NCI (non-covalent interaction) analysis. Reaction with carbon monoxide yields the corresponding mono- and dicarbonyl complexes, which display reversible binding of carbon monoxide. This equilibrium was studied by

We report on the experimental characterization of a mass-loaded silicon nitride membrane-based resonator, which we investigate towards the development of accelerometers for small amplitude acceleration sensing at low frequencies. We experimentally demonstrate a ~1.1 ×10⁻⁶ kg proof mass system achieving a 17,950 mechanical quality factor for a 526 Hz natural resonance frequency, which compares favorably to other optically interrogated on-chip accelerometers. The inferred acceleration noise floor of the device is currently limited by the displacement noise of the optical fiber displacement readout, yielding a noise amplitude spectral density of 1μg/√Hz at 10 Hz., 2022 IEEE International Symposium on Inertial Sensors and Systems (INERTIAL), May 8-11, 2022, Avignon, France

Near-field radiative heat transfer (NFHT) research currently suffers from an imbalance between numerous theoretical studies, as opposed to experimental reports that remain, in proportion, relatively scarce. Existing experimental platforms all rely on unique custom-built devices on which it is difficult to integrate new materials and structures for studying the breadth of theoretically proposed phenomena. Here we show high-resolution NFHT measurements using, as our sensing element, silicon nitride (SiN) freestanding nanomembranes$-$a widely available platform routinely used in materials and cavity optomechanics research. We measure NFHT by tracking the high mechanical quality (Q) factor ($>2\times10^6$) resonance of a membrane placed in the near-field of a hemispherical hot object. We find that high Q-factor enables a temperature resolution ($1.2\times10^{-6} \ \mathrm{K}$) that is unparalleled in previous NFHT experiments. Results are in good agreement with a custom-built model combining heat transport in nanomembranes and the effect of non-uniform stress/temperature on the resonator eigenmodes., 12 pages, 6 figures

Supplemental material, supplemental_tables_and_figures for Aging Affects the Capacity of Photoperiodic Adaptation Downstream from the Central Molecular Clock by M. Renate Buijink, Anneke H. O. Olde Engberink, Charlotte B. Wit, Assaf Almog, Johanna H. Meijer, Jos H. T. Rohling and Stephan Michel in Journal of Biological Rhythms